1. Field of the Invention
The present invention relates to a variable-displacement inclined plate compressor, and, more specifically, to a variable-displacement inclined plate compressor with an improved structure for a cam mechanism provided between a rotor and an inclined plate in the compressor.
2. Description of Related Art
Variable-displacement inclined plate compressors are known in the art. Variable-displacement inclined plate compressors are used, for example, in a refrigerating cycle of an air conditioner for vehicles. A known structure of a variable-displacement inclined plate compressor is constructed as depicted in FIG. 22. In FIG. 22, variable-displacement inclined plate compressor 100 has cylinder block 103 forming an outline of compressor housing 102, and front housing 105 closing one end of cylinder block 103. Cylinder block 103 includes a plurality of cylinder bores 101. The space enclosed by cylinder block 103 and front housing 105 forms crank chamber 104. Cylinder head 107 is attached to the other end of cylinder block 103 via valve plate 106.
Drive shaft 110 is provided to extend from the outside of front housing 105 to the inside of cylinder block 103 through boss portion 105a of front housing 105 and crank chamber 104. One end portion of drive shaft 110 is rotatably supported by bearing 108, which is provided in boss portion 105a of front housing 105. The other end portion of drive shaft 110 is rotatably supported by bearing 109, which is provided in through hole 103a defined in the central portion of cylinder block 103 to extend in the same direction as the axis of drive shaft 110. Seal member 147 is provided between boss portion 105a of front housing 105 and drive shaft 110.
Inclined plate 112 is provided around drive shaft 110 in crank chamber 104. Inclined plate 112 is slidably provided on drive shaft 110 via cylindrical sleeve 111, and rotatably attached to sleeve 111 via pin 111b and opening 111a (FIG. 23). Inclined plate 112 is rotated synchronously with drive shaft 110 via rotor 116 attached to drive shaft 110. Inclined plate 112 is variable in its inclination angle. Wobble plate 113 is provided around inclined plate 112. Wobble plate 113 is supported by inclined plate 112 via bearings 141 and 142 so that inclined plate 112 can rotate relative to wobble plate 113. The rotation of wobble plate 113 is prevented by rotation preventing mechanism 150. Rotation preventing mechanism 150 comprises guide member 144 extending along the axis direction of drive shaft 110 in crank chamber 104, and engaging member 143 provided on the outer surface of wobble plate 113 for slidably engaging guide member 144. Spring 146 is provided around drive shaft 110 between inclined plate 112 and cylinder block 103. The rotational motion of drive shaft 110 is changed to the wobble motion of wobble plate 113 via rotor 116 and inclined plate 112.
Piston 114 is inserted into each cylinder bore 101. Piston 114 is connected to wobble plate 113 via piston rod 115. One spherical end portion 115a of piston rod 115 is contained in spherical hollow portion 114a formed in piston 114. The other spherical end portion 115b of piston rod 115 is contained in spherical hollow portion 113a formed on the side surface of wobble plate 113.
Rotor 116 has arm 116a extending in a radially outward direction within a plane which includes the axis of drive shaft 110, and pivot pin 116b extending in a direction across the extending direction of arm 116a. Rotor 116 is rotatably supported on inner wall surface 105b of front housing 105 via thrust bearing 145. Inclined plate 112 has sleeve portion 112a projecting toward the side of rotor 116. Slot 112b engaging pivot pin 116b is defined in sleeve portion 112a. 
Electromagnetic clutch 120 is provided around boss portion 105a for transmitting/interrupting a driving force from an external drive source to drive shaft 110. Electromagnetic clutch 120 comprises electric magnet 123 disposed in pulley 122, which is provided on boss portion 105a via bearing 121, clutch plate 125 provided to face one end surface of pulley 122, and fastener 126 for fixing clutch plate 125 to the end of drive shaft 110.
Discharge chamber 132 and suction chamber 133 are defined in cylinder head 107, respectively, by separating the inside of cylinder head 107, closed by valve plate 106, by outer wall 131a, bottom wall 131b and inner wall 131c. Discharge chamber 132 communicates with discharge port 134, which is formed on the wall of cylinder head 107, and discharge port 106a, which is formed on valve plate 106. Suction chamber 133 communicates with suction port 135, which is formed on the wall of cylinder head 107, and suction port 106b, which is formed on valve plate 106. A suction valve (not shown) is provided on suction port 106b to cover suction port 106b. A discharge valve (not shown) and retainer 106c are provided on discharge port 106a in discharge chamber 132 to cover discharge port 106a. Control valve 117 is provided between crank chamber 104 and discharge chamber 132. Pressure control valve 117 adjusts the inclination angle of inclined plate 112 by adjusting the pressure in crank chamber 104, thereby controlling the stroke of piston 114. Thus, the displacement of the compressor is controlled by control valve 117.
In such a variable-displacement inclined plate compressor 100, when drive shaft 110 rotates, rotor 116 rotates. By the rotation of rotor 116, inclined plate 112 rotates around drive shaft 110, including wobble movement in a plane containing the axis of drive shaft 110. The rotational motion including the wobble movement of inclined plate 112 is transformed into the wobble movement of wobble plate 113 in the plane containing the axis of drive shaft 110. The wobble movement of wobble plate 113 is transformed into the reciprocal movement of piston 114 in a direction along the axis of drive shaft 110 via piston rod 115. When piston 114 moves from the position depicted in FIG. 22 to a position of the crank chamber side (left side), the fluid is drawn from suction port 135 into cylinder bore 101 through suction chamber 133 and suction port 106b. Thereafter, when piston 114 moves toward the cylinder head side (right side), the fluid in cylinder bore 101 is compressed. The compressed fluid is discharged from cylinder bore 101 to the outside of the compressor through discharge port 106a, discharge chamber 132 and discharge port 134.
FIG. 23 depicts an exploded view of the cam mechanism including rotor 116 and inclined plate 112 in compressor 100. FIG. 24 is a plan view of the assembled cam mechanism depicted in FIG. 23, and FIGS. 25 and 26 are sectional views of the cam mechanism showing the respective operational conditions.
As depicted in FIG. 23, rotor 116 is fixed to drive shaft 110. Pins 111b are inserted from the inside of sleeve 111 in the directions opposite to each other as shown by arrows, and inserted into respective holes 112d, which are defined on the inner surface of through hole 112c formed in the central portion of inclined plate 112. After sleeve 111 is fixed in through hole 112c of inclined plate 112, drive shaft 110 is inserted into sleeve 111.
As depicted in FIGS. 23 and 24, sleeve portion 112a of inclined plate 112 is inserted between arm portions 116a of rotor 116. Washers 112e are interposed between sleeve portion 112a and both arm portions 116a. Pivot pin 116b is inserted through a series of holes, which are formed by holes 116c in arm portions 116a, the holes of washers 112e and slot 112b in sleeve portion 112a. Snap rings 116d are provided on both end portions of pivot pin 116b that project through holes 116c. 
In cam mechanism 140 for a variable-displacement inclined plate compressor, inclined plate 112 and rotor 116 are connected by inserting pivot pin 116b into slot 112b formed in inclined plate 112 and holes 116c formed in rotor 116. Pivot pin 116b may be press fitted into the holes for preventing movement, or may be fixed by using snap rings 116d after insertion.
On the other hand, a cam mechanism, having a reversed positional relationship between the slot and the hole, is also known. In this type of a cam mechanism, a hole is provided in the inclined plate side, and a slot is provided in the rotor side.
FIG. 25 depicts a condition of minimum cam angle xcex8 min of cam mechanism 140 depicted in FIG. 24, namely, a condition of a minimum angle between an axis perpendicular to the axis of drive shaft 110 and inclined plate 112. In this condition, the displacement for compression of variable-displacement inclined plate compressor 100 is minimized. FIG. 26 depicts a condition of maximum cam angle xcex8 max of cam mechanism 140 depicted in FIG. 24, namely, a condition of a maximum angle between an axis perpendicular to the axis of drive shaft 110 and inclined plate 112. In this condition, the displacement for compression of variable-displacement inclined plate compressor 100 is maximized.
Thus, in known cam mechanism 140 for variable-displacement inclined plate compressor 100, the rotational force is received by the surface contact between arm portions 116a of rotor 116 and sleeve portion 112a of inclined plate 112. The reactive force of compression is received by the line contact between the inner surface of slot 112b of sleeve portion 112a and the outer surface of pivot pin 116b. 
In such a known cam mechanism 140, however, the number of parts, such as the structure for press fitting pivot pin 116b or snap rings 116d, is great, the assembly may be complicated. Therefore, improper assembly may happen. Moreover, efficient management of the parts and the assembly is difficult.
Further, a tracer control for machining slot 112b is required, and its processing is not simple. Moreover,because of a large number of parts, the cost for processing is expensive.
Further, because noise may be created during compression operation resulting from a clearance of the cam in cam mechanism 140, a shim or an increase in the processing grade of parts is required to prevent such noise.
Accordingly, it is an object of the present invention to provide an improved structure for a cam mechanism in a variable-displacement inclined plate compressor that prevents improper assembly and facilitates the efficient management of the assembly of the cam mechanism.
It is another object of the present invention to provide an improved structure for a cam mechanism in a variable-displacement inclined plate compressor that may facilitate the processing of parts and decrease the number of parts for the cam mechanism, thereby reducing the manufacturing cost.
It is a further object of the present invention to provide an improved structure for a cam mechanism in a variable-displacement inclined plate compressor that may absorb a clearance of a cam by a structure without applying a shim or increasing the processing grade of parts, thereby easily reducing a noise generated during compression operation.
To achieve the foregoing and other objects, a variable-displacement inclined plate compressor according to the present invention is herein provided. The variable-displacement inclined plate compressor includes a drive shaft, a rotor provided on the drive shaft, and an inclined plate provided around the drive shaft and rotated synchronously with the drive shaft via the rotor. The compressor comprises a cam mechanism provided between the rotor and the inclined plate for controlling an inclination angle of the inclined plate relative to an axis of the drive shaft. The cam mechanism comprises a ball which connects between the rotor and the inclined plate.
In the variable-displacement inclined plate compressor, a hole may be defined in one of the rotor and the inclined plate. A groove may be defined in the other of the rotor and the inclined plate. The ball may be contained in the hole and moved along the groove.
In the cam mechanism having such hole and groove, the hole may be formed as a semi-spherical hole, and the groove may be formed in a semi-circular cross section. In this structure, a diameter of the semi-circular cross section of the groove is preferred to be slightly larger than a diameter of the ball. Alternatively, the hole may be formed as a cylindrical hole, and the groove may be formed in a rectangular cross section. Further alternatively, the hole may be formed as a conical hole, and the groove may be formed in a triangular cross section.
In these cam mechanisms, a lubricating oil hole may be provided in at least one of the hole and the groove. Further, the shapes of the holes and grooves may be combined arbitrarily among the above-described shapes.
In the cam mechanism for the variable-displacement inclined plate compressor according to the present invention, the transmission of the driving force and the compression reactive force between the rotor and the inclined plate and the control of the inclination angle of the inclined plate are performed by the cam mechanism formed by the ball, the hole containing the ball, and the groove along which the ball moves. Because it is not necessary to use a pivot pin as in the known cam mechanism, the assembly of the cam mechanism according to the present invention is simpler. Therefore, improper assembly may be prevented. Moreover, the management of the assembly may be efficiently facilitated.
Moreover, because the number of parts in the cam mechanism is reduced as compared with that of the known mechanism, processing of the parts may be easily facilitated, and the manufacturing cost is reduced.
Further, in the cam mechanism according to the present invention, because the clearance of the cam may be automatically absorbed by the structure and the movement of the ball along the groove, any noise created during compression operation may be reduced. Further, because the ball performs a rolling motion during changing the angle of the cam (i.e., the inclination angle of the inclined plate), resistance may be very small, and the displacement of the compressor is smoothly controlled.
Further objects, features, and advantages of the present will be understood from the following detailed description of a preferred embodiment of the present invention with reference to the accompanying figures.